Field of the Invention
This invention relates generally to vehicle suspension systems combining elastic beams and torsion rods and, more particularly, to a twist isolating connection between the torsion rods and the elastic beam.
In a vehicle suspension system recently proposed by Finn and Yew, U.S. Ser. No. 516,034, filed July 22, 1983 now U.S. Pat. No. 4,540,197 and assigned to the assignee of this invention, a primary suspension elastic beam is disposed transversely of the vehicle body for bending about a pair of laterally spaced nodal points which remain stationary relative to the body. A pair of longitudinally extending torsion rods each have one end connected to a corresponding one of a pair of lower suspension control arms outboard of the pivot axes of the arms so that during jounce and rebound deflection of the control arms the torsion rods are bodily displaced in arcs about the control arm pivot axes. The elastic beam is constructed such that the ends of the beam laterally outboard of the stationary nodal points traverse arcs which approximate the arcs traversed by the arcs through the torsion rods. Accordingly, the free ends of the torsion rods are rigidly connected to the distal ends of the elastic beam so that torsional moments on the torsion rods developed by the weight of the vehicle and by suspension excursions of the control arms are resisted in beam bending by the elastic beam. While the system is inherently balanced during equal excursions of the control arms in opposite directions, unequal excursions which occur, for example, during cornering impose unbalanced forces on the system which require another pair of attachment points either between the body and the elastic beam at the nodal points or between the torsion rods and the control arms intermediate the ends of the torsion rods. In either case, but especially the second, the torsion rods may themselves experience beam bending which can twist the elastic beam about its longitudinal axis. Because elastic beams intended for operation in beam bending modes are not usually adapted for simultaneous twist about a longitudinal axis, it is desirable to isolate the elastic beam from the torsion rods with respect to such twist. A twist isolating connection according to this invention effects the desired isolation.